1. Field of the Invention
This invention relates to electrical filters and, more particularly, to an electrical filter housing that is defined cooperatively by joined filter housing sections. The invention is also directed to a method of making an electrical filter.
2. Background Art
RF filters are used widely in the cable television (CATV) industry. The filters are commonly constructed using printed circuit boards. Through frequency control, signal propagation through cable lines can be controlled. Signals from different channels can be selectively blocked by the filters so that a subscriber has access to only those channels that he/she has paid for in a particular package.
In a typical electrical filter, a printed circuit board is provided within a cylindrical housing. It is known to form the housing by combining two housing halves, each having a cable end fitting. A split housing construction facilitates the installation of the printed circuit board within a space bounded by the housing parts. With these components assembled, an electrical path is defined between the cable end fittings through the printed circuit board. Access openings are provided through the housing to allow manual electrical adjustments that permit tuning of the electrical filter. The filter construction is completed by fitting a cylindrical sleeve over the combined housing sections.
The length of the printed circuit board is determined by the particular application. Ideally, to avoid excessive component size and material waste, the filter housings are nominally matched in axial extent to the length of the printed circuit board to be contained therewithin. That is, the internal space bounded by the housing part(s) has an axial extent that will accommodate the printed circuit board while allowing an optimal spacing at the ends to facilitate electrical connection to the cable end fittings.
The need to match the dimensions of the housing and printed circuit board potentially introduces a number of inefficiencies, both from the standpoint of inventory control and manufacturing. An excess supply of a particular printed circuit board necessitates a corresponding excess supply of matched housings.
Additionally, the need to match printed circuit boards with particular housings may result in separately dedicated stations or lines to produce each, of the potentially multiple, different electrical filter designs.
Businesses that make and supply cable components are constantly striving to increase efficiencies. Heretofore, the industry has contended with the above-mentioned problems primarily because there has not been a viable design that adequately addresses these problems.